RFR: 1726: PROGRESS_MARKER should be added before the CSR bot add CSR_UPDATE_MARKER

[Zhao Song]

While testing [SKARA-1714](https://bugs.openjdk.org/browse/SKARA-1714) in this pull request (https://github.com/openjdk/playground/pull/112), we discovered that if a CSR issue already exists for a main issue and a pull request is then created for the main issue, the CSR and PR bots become stuck in an endless loop and are unable to update the pull request body. 

After further investigation, we determined that the cause of this issue is that the CSR bot checks for the presence of the CSR_UPDATE_MARKER in the pull request body before adding it, but first checks for the PROGRESS_MARKER. However, when the CSR bot's pullRequestWorkItem runs for the first time, it is likely that the PR bot's CheckWorkItem has not yet run, resulting in the absence of the PROGRESS_MARKER in the pull request body. In this case, the CSR bot continues to add the CSR_UPDATE_MARKER, while the PR bot attempts to update the pull request body but finds that it has been recently updated and therefore gives up on the update. 

The correct fix is to only add CSR_UPDATE_MARKER if we find a PROGRESS_MARKER.

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Commit messages:
 - fix test
 - SKARA-1726

Changes: https://git.openjdk.org/skara/pull/1447/files
 Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1447&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-1726
  Stats: 5 lines in 2 files changed: 2 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/skara/pull/1447.diff
  Fetch: git fetch https://git.openjdk.org/skara pull/1447/head:pull/1447

PR: https://git.openjdk.org/skara/pull/1447